A radial clamping assembly of the general type to which this invention relates comprises a hub-like tool body part that carries the cutting elements of a rotary cutting tool. The tool body part may thus comprise a hub to which a circular saw blade is securely (but usually detachably) connected, or it may comprise the body of a milling cutter or the like to which carbide tips or similar cutting elements are secured. In any case, the cutting elements of the tool are arranged in concentric relation to an axis of the tool body part, and a bore through that part that is concentric to its axis receives an untapered shaft or arbor that normally carries the tool and rotatably drives it. In the bore, which has a substantially larger diameter than the untapered shaft, there is a sleeve-like collet which normally surrounds the shaft and which provides for wedge-locking radial clamping of the tool body part to the shaft.
In a heretofore conventional radial clamping assembly, the bore through the tool body part, which had a uniform diameter along its length, terminated at each of its ends at a concentric axially and radially outwardly flared conical enlargement or countersink in the tool body part. To provide for elastic radial dilation and contraction of the collet, the collet had long, axially extending slits through it, spaced at uniform intervals around its circumference and alternately opening to one and to the other of its ends. The inside diameter of the collet, which was uniform along substantially its entire length, was large enough for the collet, in relaxed condition, to fit loosely but closely on the shaft.
Along most of the length of the collet its radially outer surface was untapered, but at one of its end portions that surface had a rather abrupt axially outward flare, thus defining a conical wedging head on the collet that was matingly received in one of the countersinks in the tool body part. At its opposite end portion, which normally projected axially beyond the tool body part, the collet had an external thread upon which a large nut was seated. In the countersink adjacent to this threaded end portion of the collet, confined between the nut and the conical countersink surface, was a split, radially elastic collar that surrounded the collet and had a conical radially outer surface. Cooperating key and keyway means on the collet and the tool body part prevented rotation of the collet relative to the body part, confining the collet to axial motion in the body part. Thus, when the nut on the threaded end portion of the collet was rotated in a tightening direction, it reacted against the split collar, shifting the collet in the axial direction to draw the conical collet head into its adjacent countersink while driving the collar into the other countersink. In this manner the countersinks effected radial contraction of the two ends of the collet whereby it was clamped to an arbor or driving shaft at the same time that it was wedgingly locked to the body part.
For removing the assembly from the shaft, as when the cutting elements of the tool needed sharpening, the nut was rotated in the opposite or loosening direction. But it often happened that the assembly was not in fact released by loosening of the nut, or even by its complete removal from the collet, because the split collar and the wedging head on the collet were tightly wedged into their respective countersinks and could be freed only with a certain amount of improvisational tapping and prying. After being released, and with the nut removed from the threaded end portion of the collet, the nut, the collet and the split collar were free to fall away from one another and the body part and could thus become lost.
The radial clamping assembly just described had been in use for many years, and the inconveniences that it presented were clearly apparent to all who came into contact with it. It is evident that those skilled in the art could find no obvious way to overcome its deficiencies.
The most nearly pertinent prior art known to the applicant is U.S. Pat. No. 4,202,644 to Soussloff (1980), U.S. Pat. No. Re. 25,318 (orig. No. 2,465,837 of 1949) to Benjamin et al, U.S. Pat. No. 2,695,787 to Sunnen (1954) and U.S. Pat. No. 2,657,933 to Stuebner (1953). While these references may be found to convey suggestions for one or another of the individual features of the present invention--which suggestions are mostly apparent to hindsight--they do not individually or in combination address the problems solved by the present invention nor suggest the combination of features by which this invention is characterized.